And now, disgruntled centrist and conservative GOP senators are forcing Senate Majority Leader Mitch McConnell to scramble to rescue the measure before debate even begins.

The Kentucky Republican was hoping to staunch his party's rebellion on Tuesday, a day after the Congressional Budget Office released its report. He plans to suggest revisions to the legislation in hopes of rounding up votes.

McConnell wants to win Senate passage this week. But three GOP senators are threatening to vote against a procedural motion to begin debate, a vote expected Wednesday. To be approved, no more than two of the 52 GOP senators can vote against it.